Make existing SSH create / remove test into a Smoke test

This particular test is a candidate for a smoke test.
This commit will close https://gitlab.com/gitlab-org/gitlab-ce/issues/52699Signed-off-by: ddavison <ddavison@gitlab.com>

qa/qa/specs/features/browser_ui/3_create/repository/add_ssh_key_spec.rb

@@ -5,7 +5,7 @@ module QA
     describe 'SSH keys support' do
       let(:key_title) { "key for ssh tests #{Time.now.to_f}" }
 
-      it 'user adds and then removes an SSH key' do
+      it 'user adds and then removes an SSH key', :smoke do
         Runtime::Browser.visit(:gitlab, Page::Main::Login)
         Page::Main::Login.act { sign_in_using_credentials }